1. Field of the Invention
The present invention relates to an apparatus and process for applying a coating medium onto a coating area of a moving substrate.
2. Description of the Related Art
German patent document DE 296 13 687 U1 discloses an apparatus which utilizes an open-jet coating mechanism. In order to define the margins of the coating area, specially designed elements are positioned in the coating gap of the open-jet coating mechanism, thus preventing the deposit of the expelled coating medium onto the fringe areas of the material web and the support roll guiding the material web. This method of defining the margins of the coating area is, from a design perspective, very complex and expensive because separate elements must be designed in a manner so they conform to the shape of the end of the LS discharge element of the respective coating mechanism and the width of the coating gap.
In light of this shortcoming, this invention provides an apparatus which can ensure a simple and cost-effective method of defining the margins of the coating area.
In the apparatus disclosed in this application, a panel element is positioned on at least one side of the two margins of the coating area, between the opening of the discharge element and the substrate, in order to prevent any deposits of the coating medium outside of the coating area, thus defining the respective margins of the coating area.
Since the panel element disclosed in this application is no longer positioned at the end of the discharge element or in the coating gap area of the coating mechanism, it also is no longer subject to the constraints imposed by these configurations. In spite of the design-related limitations imposed by the arrangement between the discharge opening and the substrate, design consideration can be given a larger degree of latitude, which, consequently, results in a less complex construction of the panel element. This has a beneficial impact not only on the selection of materials to be used, but also on the design, as far as its cost of manufacture is concerned. Furthermore, it is feasible to apply the same type of panel element to a multitude of coating mechanisms, which again reflects in lower manufacturing costs.
The application of a panel element is essentially known from German patent application 197 03 211. It differs from the panel element discussed herein by the fact that it stretches across the entire breadth of the coating area and is only inserted into the flow of coating medium exiting the coating mechanism when a splice or glue joint is about to pass through, in order to avoid a softening of the splice due to the coating medium. Thus, the familiar panel element is not inserted into the flow of coating medium expelled by the coating apparatus during the entire coating operation.
In order to guard against splash formation of the coating medium while capturing the flow of coating medium by the panel element, causing the cleanliness and quality of the respective margins of the coating area to be compromised, it is proposed, as part of a further development of this invention, that the (at least one) panel element is positioned in a manner that allows the coating medium to impact the surface of the panel element facing away from the substrate at an acute angle.
In order to provide additional protection against contamination of the surrounding area, it is further suggested to attach an end wall to the edge of the panel element that is opposite of the edge which defines the margin of the coating area. The coating medium captured by the panel element canxe2x80x94due to the surface of the panel element facing away from the substrate being shaped like the outer surface of a circular cylinderxe2x80x94easily be guided away from the moving substrate. The coating medium that has been captured can be, for example, supplied into a collecting device, which, if so desired, is shaped in the form of a collector duct for subsequent re-use.
When at least 50 percent of the length of the panel element, as measured in the direction of movement of the substrate, is positioned upstream of the (minimum of one) discharge element having been described as being part of the coating mechanism, then the coating medium, exiting at the panel element in the opposite direction relative to the feed direction, is guided away from the substrate and could be, for example, collected for later re-use.
In order to reduce the cost of manufacture, the panel element can be designed in the form of a sheet metal construction.
In order to facilitate a change in the position of the margins, it is suggested, as part of an expanded development of this invention, to include an adjusting mechanism to provide for adjusting the (minimum of one) panel element. In doing so, the panel element can be guided, i.e., by a guide rail, onto which the panel element can be fastened by use of a clamping arrangement. The adjustment can be performed either manually or with the help of a motorized drive mechanism.
The panel element described in this application can be, for example, applied in conjunction with an open-jet coating mechanism. It is, however, equally feasible to apply the panel element in conjunction with a spray coating mechanism. Also, this invention can be applied on installations that utilize a discharge opening having a shape of a single continuous channel stretching across the entire breadth of the coating area and on installations that utilize a plurality of discharge openings in the form of spray jets. The primary stipulation for the application of the panel element is solely the requirement to have a non-diminishing spacing between the moving substrate and the discharge opening of the coating mechanism.
Another aspect of this invention addresses the process for applying a liquid or viscid coating medium onto a coating area of a moving substrate by use of an apparatus having been elaborated above in various design configurations.
With the process, as is being described here, the deposit of at least a part of the coating medium being expelled by the coating mechanism onto the substrate is avoided by use of a (minimum of one) panel element during at least part of the coating duration, which thus defines the respective margins of the coating area. With respect to the advantages and any additional options associated with the process being described by this application, reference is made to the previous discussion concerning the apparatus having been designed in accordance to this invention.